System and method for detection of pulmonary embolism

ABSTRACT

Systems and methods provide for ambulatorily sensing pulmonary artery pressure from within a patient, and producing a pulmonary artery pressure measurement from the sensed pulmonary artery pressure. Power is ambulatorily provided within the patient to facilitate sensing of the pulmonary artery pressure and producing of the pulmonary artery pressure measurement. Acute pulmonary embolism is detected based on a change or rate of change in the pulmonary artery pressure measurement. An alert is preferably generated in response to detecting pulmonary embolism.

RELATED APPLICATIONS

This application claims the benefit of Provisional Patent ApplicationSer. No. 61/126,860, filed May 7, 2008, to which priority is claimedpursuant to 35 U.S.C. §119(e) and which is hereby incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates generally to detection of pulmonarydisorders, and more particularly, to systems and methods for detectingpulmonary embolism and for distinguishing acute pulmonary embolism fromother pulmonary and cardiac disorders.

BACKGROUND OF THE INVENTION

Pulmonary embolism is a common disorder accompanied by a significantmorbidity and mortality. Thromboembolism may either be acute throughactivation of the blood clotting system and disseminated intravascularcoagulation, or occur at a later stage through the formation of thrombiin the pulmonary vessels or formation in the venous circulation withsubsequent embolisation to the lung. The mortality rate for patientswith pulmonary embolism is higher than in patients with acute myocardialinfarction, exceeding 10% at 30 days and 16% at 3 months according tovarious studies. It has been estimated that pulmonary embolism accountsfor 10% of all deaths in hospitals, and is a major contributing factorin a further 10%.

Pregnant women, and in particular women undergoing caesarean section,cancer patients, trauma victims, and patients undergoing surgery (e.g.,orthopaedic surgery) are at risk. Further risk groups includeindividuals confined to bed rest or other types of confinement orrestriction in the movement of the body of limbs, both during medicaltreatment or recovery from such treatment, or during transportation,(e.g., travel by air). Further risk groups include patients withinfections and those suffering from diseases or undergoingpharmaceutical treatments that can disturb the blood clotting system orthe system for resolution of blood clots.

Deep venous thrombosis (DVT) with the attendant risk of pulmonaryembolism and post phlebitic syndrome is a frequent complication in olderpatients who have undergone surgery, suffered trauma or who have seriousillness such as malignancy or sepsis. In any category, patients who are40 years of age or older are considered to be at greatest risk. Also,the longer the period of immobilization the greater the risk of DVT.Other factors that have been reported to contribute to development ofDVT are obesity, prior history of DVT, and smoking. Heart failurepatients have increased risk of DVT on the order of three times that ofthe general population.

SUMMARY OF THE INVENTION

The present invention is directed to systems and methods for detectionof pulmonary disorders including pulmonary embolism and pulmonaryhypertension. Systems and methods of the present invention are alsodirected to discriminating between different etiologies of pulmonaryembolism and pulmonary hypertension, and between pulmonary embolism andmyocardial infarction. Systems and methods of the present invention arefurther directed to detection of acute pulmonary embolism usingpulmonary artery pressure measurements and verifying presence of acutepulmonary embolism using cardiac electrical signals.

Methods according to embodiments of the present invention involveambulatorily sensing pulmonary artery pressure from within a patient,and producing a pulmonary artery pressure measurement from the sensedpulmonary artery pressure. Power is ambulatorily provided within thepatient to facilitate the sensing of the pulmonary artery pressure andthe producing of the pulmonary artery pressure measurement. Acutepulmonary embolism is detected based on a change in the pulmonary arterypressure measurement. An alert is preferably generated in response todetecting pulmonary embolism.

Systems according to embodiments of the present invention include animplantable pressure sensor configured to ambulatorily sense pulmonaryartery pressure from within a patient. The pressure sensor preferablyincludes a support structure comprising a stabilizing arrangementconfigured to stabilize the pressure sensor within a pulmonary artery ofthe patient, a pressure transducer, and a communications device coupledto the pressure transducer. The communications device is configured toeffect wireless or wired transmission of a pulmonary artery pressurewaveform out of the patient's pulmonary artery. The pressure transducerand the communications device are supported by the support structure. Abattery is configured to supply power for the pressure transducer andthe communications device. A processor is communicatively coupled to thecommunications device of the pressure sensor. The processor isconfigured to execute programmed instructions for detecting acutepulmonary embolism based on a change in a pulmonary artery pressuremeasurement derived from the pulmonary artery pressure waveform.

The above summary of the present invention is not intended to describeeach embodiment or every implementation of the present invention.Advantages and attainments, together with a more complete understandingof the invention, will become apparent and appreciated by referring tothe following detailed description and claims taken in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure inaccordance with embodiments of the invention;

FIG. 1B is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure inaccordance with embodiments of the invention;

FIG. 1C is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure inaccordance with embodiments of the invention;

FIG. 2A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure andverification of the detected acute pulmonary embolism using a cardiacelectrical signal in accordance with embodiments of the invention;

FIG. 2B are cardiac electrical signal waveforms that show an S1Q3T3pattern that indicates presence of acute pulmonary embolism;

FIG. 3A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure anddiscriminating between acute pulmonary embolism and primary pulmonaryhypertension in accordance with embodiments of the invention;

FIG. 3B is a graph that illustrates morphological differences betweenpulmonary artery pressure waveforms associated with acute pulmonaryembolism and primary pulmonary hypertension that can be detected forpurposes of discriminating between acute pulmonary embolism and primarypulmonary hypertension in accordance with embodiments of the invention;

FIG. 4 is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure anddiscriminating between acute pulmonary embolism and myocardialinfarction in accordance with embodiments of the invention;

FIG. 5A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure anddiscriminating between acute pulmonary embolism and heart failureinduced pulmonary hypertension in accordance with embodiments of theinvention;

FIG. 5B is a graph that illustrates morphological differences betweenpulmonary artery pressure waveforms associated with acute pulmonaryembolism and heart failure induced pulmonary hypertension that can bedetected for purposes of discriminating between acute pulmonary embolismand heart failure induced pulmonary hypertension in accordance withembodiments of the invention;

FIG. 6A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure anddiscriminating between chronic pulmonary embolism and primary pulmonaryhypertension in accordance with embodiments of the invention;

FIGS. 6B and 6C show pulmonary artery pressure waveforms indicative ofchronic pulmonary hypertension and primary pulmonary hypertension,respectively, morphological differences of which may be used todiscriminate between chronic pulmonary embolism and primary pulmonaryhypertension in accordance with embodiments of the invention;

FIGS. 6D-6F illustrate features of a pulmonary artery pressure waveformthat can be used to develop indexes useful for discriminating betweenchronic pulmonary embolism and primary pulmonary hypertension inaccordance with embodiments of the invention;

FIG. 7 is a flow diagram illustrating a methodology for discriminatingbetween chronic pulmonary embolism and primary pulmonary hypertension inaccordance with embodiments of the invention;

FIG. 8A is a block diagram showing an ambulatory pulmonary arterypressure sensor in accordance with embodiments of the invention;

FIG. 8B is a block diagram showing an ambulatory pulmonary arterypressure sensor in accordance with embodiments of the invention;

FIG. 9 is a block diagram showing a system that includes an ambulatorypulmonary artery pressure sensor that may be implemented to detectpulmonary disorders and discriminate between different etiologies ofpulmonary disorders and cardiac disorders in accordance with embodimentsof the invention; and

FIG. 10 is a block diagram showing a system that includes an ambulatorypulmonary artery pressure sensor and a patient-implantable medicaldevice that may be implemented to detect pulmonary disorders anddiscriminate between different etiologies of pulmonary disorders andcardiac disorders in accordance with embodiments of the invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail below. It is to be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the invention isintended to cover all modifications, equivalents, and alternativesfalling within the scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

In the following description of the illustrated embodiments, referencesare made to the accompanying drawings, which form a part hereof, and inwhich is shown by way of illustration, various embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized, and structural and functional changes maybe made without departing from the scope of the present invention.

Systems, devices or methods according to the present invention mayinclude one or more of the features, structures, methods, orcombinations thereof described hereinbelow. For example, a device,system or method may be implemented to include one or more of theadvantageous features and/or processes described below. It is intendedthat such device, system or method need not include all of the featuresdescribed herein, but may be implemented to include selected featuresthat provide for useful structures and/or functionality. Such a device,system or method may be implemented to provide a variety of diagnosticand/or therapeutic functions.

According to embodiments of the present invention, an implantablepulmonary artery pressure sensor is configured for ambulatory sensing ofa patient's pulmonary artery pressure. Intracardiac pulmonary arterypressure indicates not only a patient's heart condition, but alsopulmonary function and respiration condition, since pulmonary arterypressure is modulated by intrathoracic pressure, which is directlyrelated to lung function.

A pulmonary artery pressure sensor of the present invention preferablyincorporates, or is otherwise coupled to, a communications device thatis capable of transmitting pulmonary artery pressure sensor informationout of the pulmonary artery. A processor is configured to executeprogrammed instructions for detecting one or more pulmonary disorders,and may also be configured to discriminate between various etiologies ofpulmonary and cardiac disorders.

In some embodiments, a patient-external system is employed to receivesensor information transmitted from the pulmonary artery pressuresensor. The patient-external system may include, for example, aprogrammer, a computing device or system such as a PC, or a hand-heldhealth care provider manipulatible device or reader. Thepatient-external system may be configured with a communications devicethat facilitates communication between a server system and thepatient-external system. Communication between the pulmonary arterypressure sensor and patient-external system may be unidirectional orbidirectional.

In system configurations that incorporate a server system, such as anadvanced patient management system, communication among the pulmonaryartery pressure sensor, patient-external system, and server system maybe any combination of unidirectional or bidirectional modalities. Theprocessor that executes programmed instructions for detecting pulmonarydisorders and discriminating between various etiologies of pulmonary andcardiac disorders may be incorporated in, or distributed among, thepulmonary artery pressure sensor, the patient-external system, and theserver system.

In other embodiments, a body implantable device, such as apatient-implantable medical device, is configured with a communicationsdevice to effect communication with the pulmonary artery pressuresensor. The communication link between the patient-implantable medicaldevice and the pulmonary artery pressure sensor may be unidirectional orbidirectional. The patient-implantable medical device incorporates acommunications device that facilitates communication between thepatient-implantable medical device and a patient-external system, whichmay further communicate with a server system. Communication among thepulmonary artery pressure sensor, patient-external system, and serversystem may be any combination of unidirectional or bidirectionalmodalities. The processor that executes programmed instructions fordetecting pulmonary disorders and discriminating between variousetiologies of pulmonary and cardiac disorders may be incorporated in, ordistributed among, the pulmonary artery pressure sensor, thepatient-implantable medical device, the patient-external system, and theserver system.

A wide variety of patient-implantable medical devices may be configuredto communicate with a pulmonary artery pressure sensor and apatient-external system in accordance with embodiments of the presentinvention. A non-limiting, representative list of such devices includesa relatively simple monitoring device that includes a communicationsdevice and memory, a nerve stimulation device, a drug delivery device,and a cardiac monitoring device. More sophisticated devices includepacemakers, cardiovertors, defibrillators, resynchronizers, and othercardiac sensing and therapy delivery devices. These devices may beconfigured with a variety of electrode arrangements, including surface,transvenous, endocardial, and epicardial electrodes (i.e., intrathoracicelectrodes), and/or subcutaneous, non-intrathoracic electrodes, andsubcutaneous array or lead electrodes (i.e., non-intrathoracicelectrodes). Such devices are referred to herein generally as apatient-implantable medical device (PIMD) for convenience, it beingunderstood that such a medical device may alternatively be implementedat least in part as a patient-external medical device.

Turning now to FIG. 1A, there is shown a flow diagram illustratingdetection of acute pulmonary embolism using ambulatorily sensedpulmonary artery pressure in accordance with embodiments of theinvention. The implementation shown in FIG. 1A involves ambulatorilysensing pulmonary artery pressure from within a patient 102, andproducing 104 a pulmonary artery pressure waveform indicative of thesensed pulmonary artery pressure. Acute pulmonary embolism is detected106 using the pulmonary artery pressure waveform. Acute pulmonaryembolism may be detected based on a change in a feature of the pulmonaryartery pressure waveform, such as a change measurable relative to athreshold. For example, detecting acute pulmonary embolism may involvedetecting a change in a morphological feature of the pressure waveformrelative to a baseline of the morphological feature established for thepatient.

The threshold may define a baseline pulmonary artery pressure valuedetermined for the patient, such as a pulmonary artery pressure value(e.g., an averaged value) measured for the patient prior to onset ofacute pulmonary embolism. Such a baseline may define a pulmonary arterypressure value for a patient that is at high risk of acute pulmonaryembolism but presently does not evidence an acute or non-acute etiologyof pulmonary embolism or pulmonary hypertension. Such a baseline maydefine a pulmonary artery pressure value for a patient that is at highrisk of acute pulmonary embolism and presently evidences a non-acuteetiology of pulmonary embolism or pulmonary hypertension, such aschronic pulmonary embolism (also referred to as chronic pulmonarythromboembolism), primary pulmonary embolism, or heart failure inducedpulmonary hypertension.

A patient's baseline pulmonary artery pressure value may alternativelybe established based at least in part on relevant patient populationdata. The relevant patient population data from which a patient'sbaseline pulmonary artery pressure value may be established is typicallydependent on whether or not a patient presently evidences a non-acuteetiology of pulmonary embolism or pulmonary hypertension, and if so,what form of pulmonary embolism or pulmonary hypertension is present. Apatient's baseline pulmonary artery pressure value may also beestablished based on a blending of patient-specific pulmonary arterypressure information and patient population data.

The threshold may also define a metric that indicates the degree ofchange or rate of change in the feature of the pulmonary artery pressurewaveform. Suitable metrics include a preestablished percent change orrate of change of the waveform feature over a specified time duration(e.g., detection window). The threshold may be defined based on othermetrics, such as standard deviation or coefficient of variation of thepulmonary artery pressure waveform feature. Suitable metrics that may bedeveloped from a variety of detectable waveform features include theabsolute value or peak of the pulmonary artery pressure waveform, theslope or trending of the slope of the pulmonary artery pressurewaveform, width of the pulmonary artery pressure waveform, fractionalpulse pressure of the pulmonary artery pressure waveform, average ormean value of the pulmonary artery pressure waveform, coefficient ofvariation or other metric involving the standard deviation, total orpartial area under the pulmonary artery pressure waveform, and timingaspects of these features. The threshold may be defined by amultiplicity of such features and/or metrics, and may involve amultiplicity of timing or detection windows associated with suchfeatures and/or metrics. The detection algorithms may use differentthresholds for different patient statuses such as indicated by othersensors' inputs. An example of the input could be an accelerometer-basedactivity sensor.

In some embodiments, acute pulmonary embolism is detected from withinthe patient. For example, a pulmonary artery pressure waveform producedambulatorily within a patient's pulmonary artery may be communicatedwirelessly from a location at which the pulmonary artery pressure issensed to a second location within the patient. The pulmonary arterypressure waveform may be communicated through a lead from the locationat which the pulmonary artery pressure is sensed to a second locationwithin the patient.

Detecting acute pulmonary embolism may be performed at the secondlocation. In other embodiments, acute pulmonary embolism is detectedexternally from the patient. By way of example, a pulmonary arterypressure waveform produced ambulatorily within a patient's pulmonaryartery may be wirelessly communicated from a location at which thepulmonary artery pressure is sensed or other patient-internal locationto a second location externally of the patient. Detecting acutepulmonary embolism may be performed at the second location.

The methodology shown in FIG. 1A is primarily directed to acutepulmonary embolism detection. However, it is considered desirable togenerate 108 an alert in response to detecting acute pulmonary embolism.The alert may be communicated to one or more of the patient, a healthcare advocate of the patient, and the patient's health care provider.The alert may take a variety of forms including an audible tone or alertmessage, a visual alert, or a signal that can be communicated to one ormore of the patient, a health care advocate of the patient, and apatient's health care provider (e.g. physician or nurse) andsubsequently converted to audible tone/message and/or a visual alert(e.g., textual, graphical, and/or sensor information). The alert ispreferably of a type that draws immediate attention to the patient'sacute pulmonary embolism condition, and indicates the seriousness ofthis condition.

The alert may be communicated via a patient-external system or deviceand/or via a patient management server system. In embodiments thatinclude a patient-implantable medical device, it may be desirable forthe PIMD to generate an alert, such as by broadcasting an audible alerttone that can be heard by the patient or health care advocate or bytransmitting an alert signal to a patient-external system and/or patientmanagement server system.

FIG. 1B is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure. Theimplementation in FIG. 1B involves ambulatorily sensing 112 pulmonaryartery pressure from within a patient, producing 114 a pulmonary arterypressure measurement from the sensed pulmonary artery pressure, anddetecting 116 acute pulmonary embolism using the pulmonary arterypressure measurement. Acute pulmonary embolism may be detected based ona change in a feature of the pulmonary artery pressure measurement, suchas a change in diastolic or systolic pressure relative to a threshold asdiscussed herein. As in the embodiment shown in FIG. 1A, it isconsidered desirable to generate 118 an alert in response to detectingacute pulmonary embolism. The alert is preferably communicated to one ormore of the patient, a health care advocate of the patient, and thepatient's health care provider.

FIG. 1C is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure. FIG. 1Cinvolves ambulatorily sensing 122 pulmonary artery pressure from withina patient, and sensing 124 a cardiac electrical signal, which may beperformed within the patient or patient-externally. Cardiac electricalsignals are analyzed by a processing system to detect phases (e.g.,systole and diastole) and/or events (e.g., end of systole, end ofdiastole) within the cardiac cycle such as systole and diastole. Thecardiac phases or events are used to determine when in the cardiac cycleto acquire 126 a pulmonary artery pressure measurement. Energy may besaved and unneeded pulmonary artery pressure samples can be avoided bysampling the pulmonary artery pressure waveform only at time(s) ofinterest. FIG. 1C further involves detecting 128 acute pulmonaryembolism using the pulmonary artery pressure measurement. As in theembodiment shown in FIGS. 1A and 1B, it is considered desirable togenerate 130 an alert in response to detecting acute pulmonary embolism.The alert is preferably communicated to one or more of the patient, ahealth care advocate of the patient, and the patient's health careprovider.

FIG. 2A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure andverification of the detected acute pulmonary embolism using a cardiacelectrical signal in accordance with embodiments of the invention. Theimplementation shown in FIG. 2A involves ambulatorily sensing pulmonaryartery pressure from within a patient 202, producing 204 a pulmonaryartery pressure waveform indicative of the sensed pulmonary arterypressure, and detecting 206 acute pulmonary embolism using the pulmonaryartery pressure waveform. Acute pulmonary embolism may be detected basedon a change in a feature of the pulmonary artery pressure waveform, suchas a change in a morphological feature of the pressure waveformmeasurable relative to a threshold as discussed above.

The methodology illustrated in FIG. 2A further involves sensing 208 acardiac electrical signal, which may be performed within the patient orpatient-externally. The cardiac electrical signals are analyzed by aprocessing system to verify 210 presence of acute pulmonary embolism asdetected by analysis of the pulmonary artery pressure information. As inthe embodiment shown in FIG. 1, it is considered desirable to generate212 an alert in response to detecting acute pulmonary embolism. Thealert is preferably communicated to one or more of the patient, a healthcare advocate of the patient, and the patient's health care provider.

In some embodiments, an implantable cardiac monitoring or stimulationdevice (e.g., PIMD) may sense electrograms or electrocardiograms (ECG).The cardiac electrical signals acquired by the PIMD may be analyzed bythe processor of the PIMD or a processor of a patient-external system toverify presence of acute pulmonary embolism as detected by analysis ofthe pressure information acquired by the pulmonary artery pressuresensor.

In other embodiments, a patient-external surface ECG recorder (e.g., a12-lead ECG recorder) may be used to acquire cardiac signals that can beanalyzed by the recorder, PC, or other patient-external processingsystem to verify presence of acute pulmonary embolism as detected byanalysis of the pressure information acquired by the pulmonary arterypressure sensor. In one configuration, the patient-external surface ECGrecorder is configured to wirelessly transmit cardiac electrical signalsto the processor that also analyzes the pulmonary artery pressureinformation, and this processor may be incorporated in a patientmanagement server system or a processor-based system local to thepatient.

FIG. 2B shows cardiac electrical waveforms acquired by use of a 12-leadECG recorder for a patient that has acute pulmonary embolism. The S1Q3T3pattern shown in FIG. 2B has been reported in a large number of patientshaving acute pulmonary embolism. In the ECG graph shown in FIG. 2B, LeadI had a large S-wave, Lead III has a large Q-wave and inverted T-wave.This characteristic pattern may be used to confirm detection of acutepulmonary embolism detected by use of ambulatorily sensed pulmonaryartery pressure information.

In one approach, a template may be produced from patient population datathat is indicative of an S1Q3T3 pattern or other pattern that indicatespresence of acute pulmonary embolism. Various known template matchingmethodologies may be used, such as those involving correlationaltechniques (e.g., feature correlation coefficient techniques) or patternrecognition, among others. According to a semi-manual approach, analgorithm may be employed that identifies presence of an S1Q3T3 patternin the ECG waveforms and adds marker channel data to a waveform displayor printout, thus allowing the health care provider to readily confirmpresence of acute pulmonary embolism as detected by analysis ofambulatorily sensed pulmonary artery pressure information acquiredimplantably from the patient. Other approaches may be used to confirmpresence of acute pulmonary embolism, such as use of MRI, X-ray, CT orother imaging technique, for example.

FIG. 3A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure anddiscriminating between acute pulmonary embolism and primary pulmonaryhypertension in accordance with embodiments of the invention. Theimplementation shown in FIG. 3A involves ambulatorily sensing pulmonaryartery pressure from within a patient 302, producing 304 a pulmonaryartery pressure waveform indicative of the sensed pulmonary arterypressure, and detecting 306 acute pulmonary embolism using the pulmonaryartery pressure waveform, such as in a manner previously discussed. Themethodology of FIG. 3A further involves discriminating 308 between acutepulmonary embolism and primary pulmonary hypertension using thepulmonary artery pressure waveform.

According to various embodiments, acute pulmonary embolism may bedistinguished from primary pulmonary hypertension based on detection ofan appreciable change of the pulmonary artery pressure signal morphologywithin a relatively short period of time. FIG. 3B shows a pulmonaryartery pressure signal 330 for a patient that has primary pulmonaryhypertension and a pulmonary artery pressure signal 320 for a patientthat experiences acute pulmonary embolism. As can be seen in FIG. 3B,the amplitude of the pulmonary artery pressure signal 330 for thepatient having primary pulmonary hypertension remains relativelyconstant or increases relatively slowly (e.g., a slow rate of change ofsignal 330) over an extended time period (e.g., days, weeks, years).

In contrast, it can be seen that the amplitude of the pulmonary arterypressure signal 320 for the patient that experiences acute pulmonaryembolism increases significantly over a relatively short time period(e.g., minutes, hours). Onset of acute pulmonary embolism may bedetected by detecting an increase in the amplitude of the pulmonaryartery pressure signal 320 (or increased rate of change of signal 320)during detection windows having a length defined in minutes or hours.

FIG. 4 is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure anddiscriminating between acute pulmonary embolism and myocardialinfarction (MI) in accordance with embodiments of the invention.Discriminating between acute pulmonary embolism and MI has traditionallybeen difficult, since these conditions have common symptoms such aschest pains and shortness of breath.

The implementation shown in FIG. 4 involves ambulatorily sensingpulmonary artery pressure from within a patient 402, producing 404 apulmonary artery pressure waveform indicative of the sensed pulmonaryartery pressure, and detecting 406 acute pulmonary embolism using thepulmonary artery pressure waveform, such as in a manner previouslydiscussed. The methodology of FIG. 4 further involves sensing a cardiacelectrical signal 408 and discriminating 410 between acute pulmonaryembolism and MI using the pulmonary artery pressure waveform and afeature of the cardiac electrical signal. The cardiac electrical signalmay be acquired in a manner discussed previously.

According to various embodiments, acute pulmonary embolism may bedistinguished from MI based on detection of an appreciable change in theST segment, T wave or Q wave of the patient's cardiac electrical. DuringMI (and assuming absence of acute pulmonary embolism onset), anelevation or depression in the ST segment, T wave inversion and/or a“significant” Q wave (e.g., an initial downward deflection of the Q waveof about 40 ms or more in any lead except III and aVR) may occur.Conversely, in the absence of MI and assuming the patient experiencesonset of acute pulmonary embolism, the ST segment and Q wave may eitherbe absent of ECG abnormalities or have different ST and Q wave patternsfrom the MI pattern, such as a gradual staircase ascent of the STinterval from S to T wave in lead 2. It is understood that MI can oftenbe detected by changes in a patient's ST segment and/or Q wave. Theeffects on the ECG due to an MI are complex but generally depend on thetype and severity of the MI. A transmural MI will commonly result inacute ST segment elevation, T-wave inversion and a significant Q wave. Asubendocardial MI will commonly result in ST segment depression and Twave inversion without evidence of significant Q waves. Acute ischemianot associated with an MI also typically acutely affects the ECG.Commonly during acute ischemia the ECG will show ST segment depression,ST segment elevation, and/or symmetrically inverted T waves. The effectsof the ischemia are temporary and the ECG returns to normal whenadequate blood flow returns to the myocardium.

FIG. 5A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure anddiscriminating between acute pulmonary embolism and heart failureinduced pulmonary hypertension in accordance with embodiments of theinvention. The implementation shown in FIG. 5A involves ambulatorilysensing pulmonary artery pressure from within a patient 502, producing504 a pulmonary artery pressure waveform indicative of the sensedpulmonary artery pressure, and detecting 506 acute pulmonary embolismusing the pulmonary artery pressure waveform, such as in a mannerpreviously discussed. The methodology of FIG. 5 further involves sensing508 a parameter indicative of heart failure and discriminating 510between acute pulmonary embolism and hear failure induced pulmonaryhypertension using the pulmonary artery pressure waveform and the heartfailure parameter.

Various parameters indicative of a patient's heart failure status may besensed within the patient or patient-externally. For example, one ormore sensors may be configured to monitor certain physiologicalparameters indicative of a patient's heart failure status (e.g.,thoracic fluid via thoracic impedance or other sensor, heart sounds,respiration, heart rate, heart rate variability, electrogram conductionpattern, blood chemistry, blood pressure, potassium levels, bloodperfusion, blood oxygen saturation, body or limb temperature, patientweight). Various system embodiments may include those that incorporateone or more implantable sensors, one or more patient-external sensor, ora combination of internal and patient-external sensors.

According to embodiments directed to implantable devices, a PIMD mayincorporate or be coupled to one or more implantable sensors. One ormore of the sensors are configured to sense a physiologic parameter orcondition indicative of the patient's heart failure status. Such sensorsmay include one or more of a thoracic impedance sensor (e.g., implantedtransthoracic total impedance sensor), a blood (internal filling)pressure sensor, blood flow sensor, blood perfusion sensor (e.g.,plethysmography sensor), blood temperature sensor, blood gas sensor(e.g., oximeter sensor), heart sounds sensor (e.g., accelerometer ormicrophone), and blood chemistry or composition sensor (e.g., PO₂sensor, SAO₂ sensor, glucose sensor, potassium sensor, lactate sensor,PCO₂ sensor, pH sensor, and molecular probe). Examples of suitable blood(internal filling) pressure sensors, blood flow sensors, bloodtemperature sensors, and associated detection techniques are describedin commonly-owned U.S. Pat. Nos. 6,666,826 and 6,892,095, which arehereby incorporated herein by reference.

A variety of external sensors may also be used to sense variousphysiological parameters that are useful for determining a patient'sheart failure status. Such external sensors may include one or more of apulse oximetry sensor, blood pressure sensor, blood chemistry sensor,patient temperature sensor, patient weight sensor, and ECG sensorarrangement, among others.

FIG. 5B is a graph that illustrates morphological differences betweenpulmonary artery pressure waveforms associated with acute pulmonaryembolism and heart failure (HF) induced pulmonary hypertension that canbe detected for purposes of discriminating between acute pulmonaryembolism and heart failure induced pulmonary hypertension in accordancewith embodiments of the invention. FIG. 5B shows a pulmonary arterypressure signal 530 for a patient that has HF induced pulmonaryhypertension and a pulmonary artery pressure signal 520 for a patientthat experiences acute pulmonary embolism. As can be seen in FIG. 5B,the amplitude of the pulmonary artery pressure signal 530 for thepatient having HF induced pulmonary hypertension increases relativelyslowly (e.g., rate of change of the signal 530) over an extended timeperiod (e.g., days, such as 1-7 days, and more particularly 1-3 days).

In contrast, it can be seen that the amplitude of the pulmonary arterypressure signal 520 for the patient that experiences acute pulmonaryembolism increases significantly over a relatively short time period, asis discussed above with reference to FIG. 3B. Onset of acute pulmonaryembolism may be detected by detecting an increase in the amplitude (orincreased rate of change) of the pulmonary artery pressure signal 520during a detection window having a length defined in minutes or hours(e.g., 15 minutes). Heart failure induced pulmonary hypertension may bedetected by detecting a change in the diastolic pulmonary arterypressure signal 530 amplitude in the range of 18 to 30 mmHg within adetection window of between about 1-7 days in length. Alternatively oradditionally, HF induced pulmonary hypertension may be detected by anincrease in the diastolic pulmonary artery pressure of about 20 to 40%within a detection window of between about 1-7 days.

FIG. 6A is a flow diagram illustrating detection of acute pulmonaryembolism using ambulatorily sensed pulmonary artery pressure anddiscriminating between chronic pulmonary embolism and primary pulmonaryhypertension in accordance with embodiments of the invention.Discriminating between chronic pulmonary embolism and primary pulmonaryhypertension is particularly useful for the health care provider inmaking the correct diagnosis and selection of possible surgicalprocedures.

The implementation shown in FIG. 6A involves ambulatorily sensingpulmonary artery pressure from within a patient 602, producing 604 apulmonary artery pressure waveform indicative of the sensed pulmonaryartery pressure, and detecting 606 acute pulmonary embolism using thepulmonary artery pressure waveform, such as in a manner previouslydiscussed. The methodology of FIG. 6A further involves discriminating608 between chronic pulmonary embolism and primary pulmonaryhypertension using the pulmonary artery pressure waveform.

FIGS. 6B and 6C show pulmonary artery pressure waveforms indicative ofchronic pulmonary embolism and primary pulmonary hypertension,respectively. Morphological differences of these waveforms may be usedto discriminate between chronic pulmonary embolism and primary pulmonaryhypertension. It has been shown that the morphology of chronic pulmonaryembolism is quite different from that of primary pulmonary hypertension.Chronic pulmonary embolism predominately involves the proximal arteries,whereas primary pulmonary hypertension primarily involves the peripheralarteries.

It is hypothesized that patient's with chronic pulmonary embolism haverelatively stiff or high resistance proximal arteries, whereas thosewith primary pulmonary hypertension have relatively stiff or highresistance peripheral arteries. These differences in the primary lesionsresults in arterial pulsatility relative to mean pressure larger in thecase of chronic pulmonary embolism than in the case of primary pulmonaryhypertension. This difference in mean pulmonary artery pressure is shownin FIGS. 6B and 6C. It can also be seen that the morphology or overallshape of the two waveforms are significantly different.

In one embodiment, primary pulmonary hypertension is distinguished fromchronic pulmonary embolism by measurement of the diastolic and systolicpulmonary pressures. If the patient's diastolic pulmonary arterypressure is greater than, for example, a range of 15 to 30 mmHg, and asystolic pulmonary artery pressure patient is greater than, for example,a range of 35 to 50 mmHG, the patient would have primary pulmonaryhypertension. If patient's diastolic pulmonary artery pressure is lessthan, for example, a range of 15 to 30 mmHg, and a systolic pulmonaryartery pressure patient is greater than, for example, a range of 35 to50 mmHG, the patient would have chronic pulmonary embolism. In anotherembodiment, if the patient's pulmonary artery pressure monotonicallydecreases from the systolic peak to the nadir of the diastolic pressurein presence of systolic pulmonary hypertension, then the patient wouldhave chronic pulmonary embolism. Alternately, if the patient's pulmonaryartery pressure has two significant peaks within a cardiac cycle and thepatient has one or more of systolic (e.g., above a range of 35 to 50mmHg) and diastolic pulmonary hypertension (e.g., above a range of 15 to30 mmHG), then the patient would have primary pulmonary hypertension.

FIGS. 6D-6F illustrate features of a pulmonary artery pressure waveformthat can be used to develop indexes useful for discriminating betweenchronic pulmonary embolism and primary pulmonary hypertension inaccordance with embodiments of the invention. To quantify theaccentuated pulsatility in the pulmonary artery pressure waveform, threeindexes may be computed and used to discriminate between chronicpulmonary embolism and primary pulmonary hypertension.

Referring to FIG. 6D, fractional pulmonary artery pulse pressure(PP_(f)) may be defined as:

${P\; P_{f}} = \frac{P\; P}{P\; A_{m}}$where PP is the pulse pressure and PA_(m) is the mean pulmonary arterypressure. Referring to FIG. 6E, coefficient of variation (CV) may bedefined as:

${C\; V} = \frac{P\; A_{SD}}{P\; A_{m}}$where PA_(SD) is the standard deviation of pulmonary artery pressure.Referring to FIG. 6F, factional time to halve the area (TA_(1/2)) may bedefined as:

${TA}_{1/2} = \frac{T_{1}}{T_{1} + T_{2}}$where T₁ is defined as the time at which the area under the pressurecurve over the T₁ period (Area₁) equals the rest of the area (Area₂).

According to the above results, criteria for differentiating chronicpulmonary embolism (CPE) and primary pulmonary hypertension (PPH) may beas follows:

-   -   If PP_(f) is greater than 1.1, then CPE, otherwise PPH;    -   If CV is greater than 0.35, then CPE, otherwise PPH;    -   If TA_(1/2) is less than 0.385, then CPE, otherwise PPH.        Detection performance can be further improved using the        following weighted index:    -   PAP_(i)=0.4*PP_(f)+0.4*CV+0.2*TA_(1/2)    -   If PAP_(i) is less than ⅔, then CPE, otherwise PPH.

FIG. 7 is a flow diagram illustrating a methodology for discriminatingbetween chronic pulmonary embolism and primary pulmonary hypertension inaccordance with embodiments of the invention. This embodiment is similarto that shown in FIG. 6A, except for the absence of detecting acutepulmonary embolism. The implementation shown in FIG. 7 involvesambulatorily sensing pulmonary artery pressure from within a patient702, producing 704 a pulmonary artery pressure waveform indicative ofthe sensed pulmonary artery pressure, and discriminating 706 betweenchronic pulmonary embolism and primary pulmonary hypertension using thepulmonary artery pressure waveform, which may be performed using themethodologies discussed above.

FIG. 8A is a block diagram showing an ambulatory pulmonary arterypressure sensor in accordance with embodiments of the invention. Thepressure sensor 802 a is preferably configured for chronic implantationwithin the pulmonary artery or vasculature proximate the pulmonaryartery. The pressure sensor 802 a is preferably of a type that canremain chronically implanted within the pulmonary artery or neighboringvasculature for an extended period of time, such as weeks, months oryears.

The pressure sensor 802 a shown in FIG. 8A includes a pressuretransducer 804, a communications device 808, and a power circuit 806.The pressure sensor 802 a is configured for implantation within apatient's pulmonary artery or vasculature proximate the pulmonaryartery. A power source of the power circuit 806 ambulatorily providespower for pressure sensor circuitry 802 a and the communications device808. The pressure transducer 804 may include an accelerometer, a MEMSsensor, strain gauge, piezoresistive, capacitive, transductive, or othertype of pressure transducer.

According to other embodiments, pulmonary artery pressure may beimplantably and ambulatorily measured without entering the pulmonaryartery. According to one implementation, wall deflections of thepulmonary artery can be measured via a vessel adjacent to the pulmonaryartery. The arterial wall deflections can be used to detect systolicblood pulses and measure various parameters of the cardiac output andarterial blood flow. Use of such a sensor measures wall deflections of avessel adjacent to the pulmonary artery, and as such, a pulmonary arterypressure measurement can be conducted without invasively disturbing thepulmonary artery. A suitable sensor for this application is disclosed incommonly owned U.S. Publication No. 2009/0088651, which is incorporatedherein by reference.

The communications device 808 is coupled to the pressure transducer 804,and is configured to effect wireless transmission 810 of a pulmonaryartery pressure waveform out of the patient. The communications device808 may comprise, for example, an ultrasonic, acoustic, inductive,optical or RF communications device. The power circuit 806 may include abattery or other energy source, which may be primary (non-rechargeable),chargeable or rechargeable. For example, the power circuit 806 mayinclude an energy harvesting (EH) device that is excited by bodymovement, thermal changes, and/or acoustic pressure waves, such as isdescribed in U.S. Pat. Nos. 7,283,874 and 7,283,874, which areincorporated herein by reference. Energy acquired by the EH device isconverted to electrical current that is stored in a battery of the powercircuit 806.

In other configurations, the power circuit 806 may include an inductivecircuit that can be excited by a patient-external source, such as adrive coil or magnet arrangement that radiates a magnetic field. Theinductive circuit charges a battery of the power circuit 806 in responseto an externally generated magnetic field.

According to one approach, a tank circuit may be implemented in thepower circuit 806 that is configured to collect energy from a magneticfield generated by a drive coil or coils of a patient-externalrecharging unit. The drive coil(s) preferably generate a continuous ordiscontinuous harmonic magnetic field. The tank circuitry is preferablytuned to resonate at the frequencies that the drive coil(s) are driven.In one illustrative example, the tank circuitry may include two tankcircuits set to resonate at different frequencies, such as 90 kHz and160 kHz, respectively. Each of the resonant tank circuits buildsamplitude during a burst produced by the drive coil(s) and thengradually loses signal amplitude after the drive coil(s) is turned off.The time associated with the exponential charging and discharging of theresonant tank circuits is determined by the capacitive and inductiveelements in the tank circuits.

One or both of the two coils may be used to generate power for thepressure sensor 802 a via an appropriate power regulator or convertercircuit (e.g., AC-to-DC converter). In other configurations, one of thecoils may be used to generate power while the other is used to transmitpressure sensor data to a patient-external device. Sensor data may beencoded on a waveform that radiates from a transmission circuit drivenby the second coil. The data may modulate the waveform and decoded by anenvelope detector circuit (e.g., which may include synchronousdemodulators) of the patient-external system using known techniques. Inthis approach, resonant circuitry of the pressure sensor 802 a providesfor power and communications channels for the sensor 802 a.

The pressure transducer 804, communications device 808, and powercircuit 806 are supported by a support structure. The support structurecomprises a stabilizing arrangement configured to stabilize the pressuresensor 802 a within the pulmonary artery. For example, the supportstructure of the pressure sensor 802 a may comprise a stent graftconfigured to radially contract during implantation in a pulmonaryartery and expand to stabilize the pressure sensor at an implant sitewithin a pulmonary artery. A suitable stent graft support structure isdisclosed in U.S. Pat. No. 6,840,956, which is incorporated herein byreference. Other support structures may be employed, such as hooks onthe end of struts contacting the intima of the vessel or a helix placedlongitudinally in the vessel and exerting radial force on the intima ofthe vessel.

FIG. 8B is a block diagram showing an ambulatory pulmonary arterypressure sensor 802 b in accordance with embodiments of the invention.The pressure sensor 802 b shown in FIG. 8B is similar to that of FIG.8A, but further includes a processor 815. The processor 815 iscommunicatively coupled to the pressure transducer 804 andcommunications device 808 of the pressure sensor 802 b. The processor815 may be configured to execute programmed instructions for detectingacute pulmonary embolism and/or discriminating between variousetiologies of pulmonary and cardiac disorders in a manner previouslydescribed.

Suitable pressure sensors and approaches for communicating sensorinformation that may be implemented in accordance with the presentinvention are disclosed in U.S. Pat. Nos. 6,277,078; 6,764,446;7,198,603; 7,273,457; 7,198,603; 7,572,228 and 7,641,619 and in USPublished Application Nos. 2007/0129637 and 2007/0274565, which areincorporated herein by reference.

FIG. 9 is a block diagram showing a system that includes an ambulatorypulmonary artery pressure sensor that may be implemented to detectpulmonary disorders and used to discriminate between differentetiologies of pulmonary and cardiac disorders in accordance withembodiments of the invention. The system shown in FIG. 9 includes animplantable pulmonary artery pressure (PAP) sensor 802 shown implantedwithin a pulmonary artery 903 or vasculature proximate the pulmonaryartery. The PAP sensor 802 may be configured in the manner shown in FIG.8A or 8B. The PAP sensor 802 transmits pressure information via acommunications link 810 through the patient's body (via skin surface905) for reception by a patient-external system 910.

The patient-external system 910 includes a communications device 914 andmay optionally include a recharging unit 912. The optional rechargingunit 912 may be configured in a manner discussed previously to provide asource for energizing a charging circuit within the PAP sensor 802. Thepatient-external system 910 may be configured as, or communicate with, avariety of devices, sensors, and systems. For example, thepatient-external system 910 may be configured to communicate withvarious sensors and devices, such as a weight scale (not shown), bloodpressure cuff (not shown), pulse oximeter (not shown), or drug deliverydevice (not shown). The patient-external system 910 may be configured tocommunicate with a patient management server 925, PDA 920, PC 930, cellphone 935 or a programmer 940.

In other embodiments, the patient-external system 910 may be configuredas, or otherwise be incorporated as part of, a PDA 920, PC 930, cellphone 935, or a wired (link 957) or wireless (link 953) hand-held reader950. Such devices that are configured to ambulatorily receive pulmonaryartery pressure information have the advantages of being highly portableand capable of communicating patient information, including PAP sensorinformation, to a remote location (e.g., patient management server 925)via existing communications infrastructure. Methods, structures, and/ortechniques described herein, which may be adapted to provide for remotepatient/device monitoring, diagnosis, therapy, or other APM relatedmethodologies, may incorporate features of one or more of the followingreferences: U.S. Pat. Nos. 6,221,011; 6,270,457; 6,277,072; 6,280,380;6,312,378; 6,336,903; 6,358,203; 6,368,284; 6,398,728; and 6,440,066,which are hereby incorporated herein by reference.

In some configurations, a wired or wireless hand-held reader 950 maycooperate with a programmer 957 or other system. In otherconfigurations, the hand-held reader 950 may be configured to operateexclusive of a programmer or other system. For example, the hand-heldreader 950 may be configured to receive pressure sensor informationdirectly from the PAP sensor 802. The pressure sensor information may bestored in a memory of the hand-held reader 950. Alternatively or inaddition, a processor of the hand-held reader 950 may be configured toexecute programmed instructions for detecting acute pulmonary embolismand/or discriminating between various etiologies of pulmonary andcardiac disorders in a manner previously described. The hand-held reader950 may include a user interface with which to interact with the PAPsensor 802 (e.g., interrogate the sensor, perform sensor diagnostics,modify firmware if equipped with a processor or controller) and/or aprogrammer, server system or other device/system. The user-interface ofthe hand-held reader 950 may include a display for displaying pressuresensor data and discrimination data, among other information.

FIG. 10 is a block diagram showing a system that includes an ambulatorypulmonary artery pressure sensor and a patient-implantable medicaldevice that may be implemented to detect pulmonary disorders anddiscriminate between different etiologies of pulmonary disorders inaccordance with embodiments of the invention. FIG. 10 is similar to thesystem shown in FIG. 9, but further incorporates a PIMD 901 that isconfigured to communicate wirelessly with the PAP sensor 802 via link907. In other configurations, including those shown in other figures,the PIMD 901 is configured to communicate through a lead 908 with thePAP sensor 802, such as is described in commonly owned US PublishedApplication No. 2004/0260374, which is hereby incorporated herein byreference.

The PIMD 901 may include a processor that receives sensor informationfrom the PAP sensor 802 and executes programmed instructions fordetecting acute pulmonary embolism and/or discriminating between variousetiologies of pulmonary and cardiac disorders in a manner previouslydescribed. The PIMD 901 may transmit the pulmonary artery pressureinformation and/or the detection/discrimination output to thepatient-external system 910.

The PIMD 901 may be implemented to communicate with the patientmanagement server 925 or network via the patient-external system 910 oran appropriate communications interface. The PIMD 901 may be used withinthe structure of an advanced patient management (APM) system. Theadvanced patient management system allows health care providers toremotely and automatically monitor pulmonary and cardiac functions, aswell as other patient conditions. In one example, a PIMD implemented asa monitor, pacemaker, defibrillator, or resynchronization device may beequipped with various telecommunications and information technologiesthat enable real-time data collection, diagnosis, and treatment of thepatient. Other PIMD embodiments described herein may be used inconnection with advanced patient management.

By way of example, PIMD 901 may incorporate heart failure featuresinvolving dual-chamber or bi-ventricular pacing/therapy, cardiacresynchronization therapy, cardiac function optimization, or other heartfailure related methodologies. For example, PIMD 901 may incorporatefeatures of one or more of the following references: commonly owned USPublished Application No. 2003/0130702 and U.S. Pat. Nos. 6,411,848;6,285,907; 4,928,688; 6,459,929; 5,334,222; 6,026,320; 6,371,922;6,597,951; 6,424,865; and 6,542,775, each of which is herebyincorporated herein by reference.

Certain configurations of the PIMD 901 may incorporate various functionstraditionally performed by an implantable cardioverter/defibrillator(ICD), and may operate in numerous cardioversion/defibrillation modes asare known in the art. Examples of ICD circuitry, structures andfunctionality, aspects of which may be incorporated in embodiments ofthe PIMD 901 are disclosed in commonly owned U.S. Pat. Nos. 5,133,353;5,179,945; 5,314,459; 5,318,597; 5,620,466; and 5,662,688, which arehereby incorporated herein by reference.

Various configurations of the PIMD 901 may incorporate functionstraditionally performed by pacemakers, such as providing various pacingtherapies as are known in the art, in addition to, or exclusive of,cardioversion/defibrillation therapies. Examples of pacemaker circuitry,structures and functionality, aspects of which may be incorporated inembodiments of the PIMD 901 are disclosed in commonly owned U.S. Pat.Nos. 4,562,841; 5,284,136; 5,376,106; 5,036,849; 5,540,727; 5,836,987;6,044,298; and 6,055,454, which are hereby incorporated herein byreference.

The PIMD 901 may implement diagnostic and/or monitoring functions aswell as, or exclusive of, providing cardiac stimulation therapy.Examples of cardiac monitoring circuitry, structures and functionality,aspects of which may be incorporated in embodiments of the PIMD 901 aredisclosed in commonly owned U.S. Pat. Nos. 5,313,953; 5,388,578; and5,411,031, which are hereby incorporated herein by reference.

The terms “ambulatory” and “ambulatorily” that modify the termspulmonary artery pressure sensor and sensing pulmonary artery pressure,respectively, are intended to connote implementations in which apressure sensor is chronically implanted in a patient's pulmonaryartery. Provision of a chronically implanted pulmonary artery pressuresensor of the present invention, in contrast to an acute pulmonaryartery pressure sensing approach, allows the patient to go about his orher normal routine for extended periods of time, unencumbered bycatheters and/or temporary percutaneously sensing apparatuses that aretypically used in a hospital setting for conducting short-term invasiveclinical evaluations lasting on the order of hours (e.g., 1-10 hours,but <24 hours). In the context of various presently claimed embodiments,a chronically implanted pressure sensor provides for ambulatory sensingof a patient's pulmonary artery pressure for days (e.g., >30 days),weeks, months, or years.

Various modifications and additions can be made to the preferredembodiments discussed hereinabove without departing from the scope ofthe present invention. Accordingly, the scope of the present inventionshould not be limited by the particular embodiments described above, butshould be defined only by the claims set forth below and equivalentsthereof.

What is claimed is:
 1. A method, comprising: ambulatorily sensingpulmonary artery pressure from within a patient; producing a pulmonaryartery pressure measurement from the sensed pulmonary artery pressure;ambulatorily providing power within the patient to facilitate thesensing of the pulmonary artery pressure and the producing of thepulmonary artery pressure measurement; detecting acute pulmonaryembolism based on a change in the pulmonary artery pressure measurement;and discriminating, using a processor, between acute pulmonary embolismand primary pulmonary hypertension based on a rate of change of thepulmonary artery pressure measurement.
 2. The method of claim 1,comprising sensing a cardiac electrical signal, wherein timing of thepulmonary artery pressure measurement is based at least in part on thesensed cardiac electrical signal.
 3. The method of claim 1, comprisingproducing a pulmonary artery pressure waveform indicative of the sensedpulmonary artery pressure, wherein the pulmonary artery pressuremeasurement is derived from the pulmonary artery pressure waveform. 4.The method of claim 3, wherein detecting acute pulmonary embolismcomprises detecting acute pulmonary embolism based on a change in afeature of the pulmonary artery pressure waveform relative to athreshold, the feature comprising a morphological feature of thepressure waveform and the threshold comprising a baseline of themorphological feature established for the patient.
 5. The method ofclaim 1, wherein detecting acute pulmonary embolism comprises detectingacute pulmonary embolism based on the change in the pulmonary arterypressure measurement relative to a threshold, the threshold comprising abaseline pulmonary artery pressure value determined for the patientusing at least one of patient specific data and patient population dataindicative of acute pulmonary embolism.
 6. The method of claim 1,wherein detecting acute pulmonary embolism comprises detecting acutepulmonary embolism from within the patient.
 7. The method of claim 1,wherein detecting acute pulmonary embolism comprises detecting acutepulmonary embolism externally from the patient.
 8. The method of claim1, comprising wirelessly communicating the pulmonary artery pressuremeasurement from a location at which the pulmonary artery pressure ismeasured to a second location within the patient, wherein detectingacute pulmonary embolism comprises detecting acute pulmonary embolism atthe second location.
 9. The method of claim 1, comprising wirelesslycommunicating the pulmonary artery pressure measurement from a locationat which the pulmonary artery pressure is measured to a second locationexternally of the patient, wherein detecting acute pulmonary embolismcomprises detecting acute pulmonary embolism at the second location. 10.The method of claim 1, comprising facilitating wired communication ofthe pulmonary artery pressure measurement from a location at which thepulmonary artery pressure is measured to a second location within thepatient, wherein detecting acute pulmonary embolism comprises detectingacute pulmonary embolism at the second location.
 11. The method of claim1, comprising: sensing a cardiac electrical signal; and discriminatingbetween acute pulmonary embolism and myocardial infarction based on achange of the pulmonary artery pressure measurement relative to a changein a feature of the sensed cardiac electrical signal.
 12. The method ofclaim 11, wherein the feature of the sensed cardiac electrical signalcomprises an ST segment of the sensed cardiac electrical signal, anddiscriminating between acute pulmonary embolism and myocardialinfarction comprises: detecting myocardial infarction as a change in afeature of the ST segment; and detecting acute pulmonary embolism as achange in the pulmonary artery pressure measurement in the absence of anappreciable change in the ST segment feature or other myocardialinfarction-associated feature of the sensed cardiac electrical signal.13. The method of claim 1, comprising: sensing a parameter indicative ofheart failure from within the patient; and discriminating between acutepulmonary embolism and heart failure induced pulmonary hypertensionbased on the rate of change of the pulmonary artery pressure measurementand a change in the sensed parameter.
 14. The method of claim 1,comprising sensing cardiac electrical signals and verifying detection ofacute pulmonary embolism using the sensed cardiac electrical signals.15. The method of claim 1, comprising generating an alert in response todetection of acute pulmonary embolism, and communicating the alertoutside of the patient's body.
 16. A system, comprising: an implantablepressure sensor configured to ambulatorily sense pulmonary arterypressure from within a patient, the pressure sensor comprising: asupport structure comprising a stabilizing arrangement configured tostabilize the pressure sensor within a pulmonary artery of the patient;a pressure transducer; a communications device coupled to the pressuretransducer, the communications device configured to effect wirelesstransmission of a pulmonary artery pressure waveform out of thepatient's heart, the pressure transducer and the communications devicesupported by the support structure; and a battery configured to supplypower for the pressure transducer and the communications device; and aprocessor communicatively coupled to the communications device of thepressure sensor, the processor executing programmed instructions fordetecting acute pulmonary embolism based on a change in a pulmonaryartery pressure measurement derived from the pulmonary artery pressurewaveform, the processor executing programmed instructions fordiscriminating between acute pulmonary embolism and primary pulmonaryhypertension based on a rate of change of the pulmonary artery pressuremeasurement.
 17. The system of claim 16, wherein the processor isdisposed in a body implantable housing, the body implantable housingcomprising a communications device configured to effect wirelesscommunications between the processor and the communications device ofthe pressure sensor.
 18. The system of claim 16, wherein the processoris disposed in a body implantable housing and coupled to thecommunications device of the pressure sensor via a lead.
 19. The systemof claim 16, wherein the processor is disposed in a body implantablehousing, the system comprising a patient-external system comprising acommunications device configured to effect wireless communications withthe processor.
 20. The system of claim 16, wherein the processor isdisposed in a patient-external system, the patient-external systemcomprising a communications device configured to effect wirelesscommunications with the communications device of the pressure sensor.21. The system of claim 16, comprising a portable patient-externalsystem disposed in a housing configured for hand-held manipulation and apatient-external server system, the housing of the portablepatient-external system comprising communications circuitry configuredto effect wireless communications with the communications device of thepressure sensor and communications with the patient-external serversystem, the processor disposed in at least one of the housing of theportable patient-external system and the patient-external server system.22. The system of claim 16, wherein the implantable pressure sensorcomprises a charging circuit responsive to an acoustic or inductivesignal, the charging circuit generating energy for powering the pressuresensor in response to the acoustic or inductive signal.
 23. The systemof claim 16, wherein the support structure of the pressure sensorcomprises a stent graft configured to radially contract duringimplantation in the pulmonary artery and expand to stabilize thepressure sensor at an implant site within the pulmonary artery.
 24. Thesystem of claim 16, wherein the communications device coupled to thepressure sensor comprises an acoustic communications device.
 25. Thesystem of claim 16, wherein the communications device coupled to thepressure sensor comprises at least one of an inductive, optical, or RFcommunications device.
 26. The system of claim 16, comprising a sensorconfigured to sense a cardiac electrical signal, wherein the processorexecutes programmed instructions for discriminating between acutepulmonary embolism and myocardial infarction based on a change of thepulmonary artery pressure waveform relative to a change in a feature ofthe sensed cardiac electrical signal.
 27. The system of claim 26,wherein the feature of the sensed cardiac electrical signal comprises afeature of an ST segment of the sensed cardiac electrical signal,wherein the processor executes programmed instructions for detectingmyocardial infarction as a change in the ST segment feature and fordetecting acute pulmonary embolism as a change in the pulmonary arterypressure measurement in the absence of an appreciable change in the STsegment feature or other myocardial infarction-associated feature of thesensed cardiac electrical signal.
 28. The system of claim 16, comprisinga sensor configured to sense a parameter indicative of heart failurefrom within the patient, wherein the processor executes programmedinstructions for discriminating between acute pulmonary embolism andheart failure induced pulmonary hypertension based on the rate of changeof the pulmonary artery pressure measurement and a change in the sensedparameter.
 29. The system of claim 16, comprising a sensor configured tosense a cardiac electrical signal, wherein the processor executesprogrammed instructions for verifying detection of acute pulmonaryembolism using the sensed cardiac electrical signals.
 30. A method,comprising: ambulatorily sensing pulmonary artery pressure from within apatient; producing a pulmonary artery pressure measurement from thesensed pulmonary artery pressure; ambulatorily providing power withinthe patient to facilitate the sensing of the pulmonary artery pressureand the producing of the pulmonary artery pressure measurement;detecting acute pulmonary embolism based on a change in the pulmonaryartery pressure measurement; and discriminating, using a processor,between chronic pulmonary embolism and primary pulmonary hypertensionbased on one or more of a fractional pulse pulmonary artery pressurederived from a waveform indicative of the sensed pulmonary arterypressure, a coefficient of variation of the pulmonary artery pressurederived from the pulmonary artery pressure waveform, and a fractionaltime to half the area under the pulmonary artery pressure waveform. 31.A system, comprising: an implantable pressure sensor configured toambulatorily sense pulmonary artery pressure from within a patient, thepressure sensor comprising: a support structure comprising a stabilizingarrangement configured to stabilize the pressure sensor within apulmonary artery of the patient; a pressure transducer; a communicationsdevice coupled to the pressure transducer, the communications deviceconfigured to effect wireless transmission of a pulmonary arterypressure waveform out of the patient's heart, the pressure transducerand the communications device supported by the support structure; and abattery configured to supply power for the pressure transducer and thecommunications device; and a processor communicatively coupled to thecommunications device of the pressure sensor, the processor executingprogrammed instructions for detecting acute pulmonary embolism based ona change in a pulmonary artery pressure measurement derived from thepulmonary artery pressure waveform, the processor executing programmedinstructions for discriminating between chronic pulmonary embolism andprimary pulmonary hypertension based on one or more of a fractionalpulse pulmonary artery pressure derived from the pulmonary arterypressure waveform, a coefficient of variation of the pulmonary arterypressure derived from the pulmonary artery pressure waveform, and afractional time to half the area under the pulmonary artery pressurewaveform.